Truncating Mutation In Exon Research Articles

Oxidative stress-induced apoptosis in two patients with Alagille syndrome

Alagille syndrome (AGS) is an autosomal dominant disorder characterized by cholestasis, cardiac, skeletal and ocular abnormalities. Increasing importance is being given to vascular and central nervous system impairment. AGS is in most cases caused by heterozygous mutations in the Jagged-1 (JAG1) gene encoding a cell-surface ligand of the Notch receptors. The interaction between Notch1 and JAG1 induces proliferation and inhibits apoptosis. We evaluated the role of apoptosis in AGS patients carrying a truncating mutation in exon 7 of JAG1. Peripheral blood lymphocytes (PBLs) from two patients were exposed to 2-deoxy-d-ribose (dRib). Apoptosis was analyzed by flow cytometry, fluorescence microscopy and Western blotting. PBLs from patients showed a significantly higher percentage of apoptosis than controls both in standard culture conditions and after dRib treatment, however we demonstrated a lack of caspase-8 activation in those cells. Our results confirm that JAG1 may play a role in apoptosis regulation. In particular, truncating mutations in JAG1 could lead to Notch signaling inhibition and determine a deregulation of survival and proliferation, favoring apoptosis. Moreover, the lack of caspase-8 activation in AGS patients indicates a possible selective impairment of caspase-8 cleavage suggesting that JAG1 plays a specific role in the regulation of caspase-8 activation.

A novel homozygous COL11A2 deletion causes a C‐terminal protein truncation with incomplete mRNA decay in a Turkish patient

Recessive mutations in COL11A2 (collagen, type XI, alpha 2), are responsible for otospondylomegaepiphyseal dysplasia (OSMED) and non-syndromic hearing loss while dominant mutations are associated with Stickler type III, isolated cleft palate, Robin sequence, non-ophthalmic Stickler syndrome, early onset osteoarthritis and autosomal dominant hearing loss. We describe here the clinical findings of two Turkish cousins with OSMED carrying a novel homozygous truncating mutation in exon 38 of COL11A2 gene, c.2763delT, identified on cDNA and confirmed at gDNA. This mutation is located on triple helix repeat domain of the collagen alpha-2(XI) chain, where the majority of the previously identified mutations are located. Real-time RT-PCR experiment provided that mutated transcript does not decay completely. Although our analysis displays the partial survival of the mutant transcript from blood tissue, not from cartilage, we propose that this mechanism may play an important role on the variable expressivity of the heterozygous COL11A2 gene mutations.

Novel dermatological manifestations of Mowat–Wilson syndrome including photosensitivity and dyspigmentation

The authors update on a previously reported patient with Mowat–Wilson syndrome (MWS) with unusual dermatological features including photosensitivity and skin dyspigmentation.1 An 18-month-old Afro-Caribbean boy with Hirschsprung9s disease, hypospadias, delayed visual maturation, microcephaly, developmental delay, seizures and dysmorphic facial features was referred to the dermatology department. Since birth he displayed persistent skin dyspigmentation with patchy macular hypo- and hyperpigmentation involving the face and neck, upper limbs, trunk, perineum and right ankle. There was no history of preceding inflammation or eczema. Following the original report, his parents have described photosensitivity since the age of 2 years, with sunburn-like erythema occurring within minutes of sun exposure despite application of high-factor sunblock. Investigations including lupus serology and porphyria screen were normal. The patient is currently awaiting formal phototesting. Genetic analysis previously identified a heterozygous truncating mutation in exon 8 of the ZEB2 (formerly ZFHXIB; Zinc finger homeobox 1B) gene, confirming MWS. MWS was first described in 1998, comprising characteristic facial dysmorphism, profound learning difficulties, epilepsy, Hirschprung9s disease and other congenital abnormalities, mapped to a locus at chromosome 2q21–q23.2 In 2001 the causative gene, ZEB2 was identified.3 Subsequently, over 100 pathogenetic heterozygous mutations or deletions are described.4 The distinctive evolving facial phenotype has been recently reviewed.5 ZEB2 encodes Smad interacting protein (SIP1), a ubiquitous transcription factor with an important role in embryological development including the neural crest. “Raindrop” pigmentation has been previously reported in a 9-year-old patient with MWS.6 This indicates that MWS should be added to the spectrum of neurocutaneous disorders comprising dyspigmentation and Hirschprung9s. We can speculate that dyspigmentation results from ZEB2 haploinsufficiency disrupting neural crest melanocyte development or migration. Our case is the first record of photosensitivity in MWS, raising the possibility of an additional role of ZEB2 in regulating the cutaneous response to ultraviolet radiation.

Molecular and clinical analysis of Ellis-van Creveld syndrome in the United Arab Emirates

BackgroundEllis-van Creveld (EvC) syndrome is an autosomal recessive chondrodysplastic condition with clinical manifestations that include short-limbs and ribs, postaxial polydactyly and dysplastic nails and teeth. In about two thirds of patients, mutations in either EVC or EVC2 genes have been found to be the underlying cause.MethodsIn this paper, we describe the molecular (DNA sequencing) and clinical analysis of six children diagnosed with EvC from four different families from the United Arab Emirates (UAE).ResultsAll the children had the common clinical and radiological features of this syndrome. However, DNA sequence analysis of the genes shown to be involved (EVC and EVC2) revealed a novel splice site mutation (c.2047-1G>T) in intron 13 of EVC2 gene in one family. In addition, we confirm previous mutational analyses that showed a truncating mutation in exon 13 of EVC gene (c.1813C>T; p.Q605X) in the second family and a single nucleotide deletion (c.981delG; p.K327fs) in exon 8 of EVC2 gene in the third family. No mutations in the exons, splice sites or the promoter regions of either gene have been found in the index case of the fourth family who exhibited "EvC-like" features.ConclusionsGiven the small population size of UAE, our data illustrates further the molecular heterogeneity observed in EvC patients and excludes the possibility of a common founder effect for this condition in the UAE reflecting the current ethnic diversity of the country.

Severe Infantile Carnitine Palmitoyltransferase II Deficiency in 19-Week Fetal Sibs

Antenatal presentation of carnitine palmitoyltransferase type II deficiency due to mutations in the CPT2 gene has been rarely reported. We report an Ashkenazi Jewish family with 3 terminated pregnancies for multicystic kidneys and/or hydrocephalus. Fetal autopsy after termination of the couple's 4th pregnancy (sib 2) showed renal parenchyma replaced by cysts that appeared to increase in diameter toward the medulla. Fetopsy after termination of the 7th pregnancy (sib 3) revealed micrognathia; hypospadias; cystic renal dysplasia; hepatosteatosis; and lipid accumulation in the renal tubular epithelium, myocardium, and skeletal muscle. Microvascular proliferative changes and focal polymicrogyria were seen in the brain. A beta-oxidative enzyme deficiency was suspected. CPT2 gene analysis showed a homozygous complex haplotype for the F448L mutation associated with a c.del1238_1239AG (p.Q413fs) truncating mutation in exon 4. Carnitine palmitoyltransferase type II deficiency should be included in the differential diagnosis in fetuses of Ashkenazi origin with multicystic kidneys and unusual cerebral findings.

Combined Retinal Hamartomas Leading to the Diagnosis of Neurofibromatosis Type 2

Purpose: To report two cases of neurofibromatosis type 2 (NF2) initially presenting with isolated bilateral combined hamartomas of the retina and retinal pigment epithelium (RPE). Methods: Retrospective observational case reports. Results: Two unrelated children presented to ophthalmology with isolated combined hamartomas of the retina and RPE. Patient one presented to ophthalmology at the age of 2 years; by 4 years, he developed what was thought to be a plexiform neurofibroma and, with more than 6 café au lait spots, was diagnosed with neurofibromatosis type 1 (NF1). By the age of 5, he had developed bilateral vestibular schwannomas, and was diagnosed with NF2. Subsequent molecular testing revealed a truncating mutation in exon 13 (c.1396C > T; p.R466X) of the NF2 gene. Patient two presented to ophthalmology at the age of 7 months; by age 6 she had developed two subcutaneous masses on her forehead, a mass in her left lower abdomen, and in her gumline. Despite lack of pathological evidence of neurofibroma upon biopsy, molecular testing was initiated at age 6 and revealed a truncating mutation in exon 8 (c.734delA) of the NF2 gene in the blood. Conclusions: Bilateral combined hamartomas of the retina and retinal pigment epithelium (RPE) in a young child should alert the clinician to the possibility of neurofibromatosis type 2. The recognition of this rare finding as a presenting feature of NF2 can lead to earlier diagnosis, which is vital to appropriate surveillance and possible surgical intervention.

The first prenatal diagnosis for veno‐occlusive disease and immunodeficiency syndrome, an autosomal recessive condition associated with mutations in SP110

We present the first prenatal diagnosis of familial hepatic veno-occlusive disease with immunodeficiency (VODI). Homozygous mutations in the gene SP110 are the genetic basis of VODI. The proband in this report presented at three months of age with hepatomegaly hepatic failure and was found to have hypogammaglobulinemia. He died one month after hepatic transplant at eight months of age due to hemophagocytic syndrome. DNA testing detected a homozygous truncating mutation in exon 5; SP110 c.642delC. Prenatal testing was offered to this family in a subsequent pregnancy. Chorion villus was sampled at 12 weeks' gestation. DNA was extracted using standard techniques, and sequencing of SP110 exon 5 was performed using flanking primers. Maternal contamination was excluded by examining STR markers in CVS and maternal DNA. A heterozygous SP110 c.642delC mutation was detected in exon 5. This mutation was present in heterozygous form in both parents. The prenatal test result is predictive of a child with a normal immune and hepatic phenotype. This report presents the first prenatal molecular diagnosis for VODI and shows the importance of molecular genetic research in not only defining the aetiology of syndromes but also in assisting reproductive choices through the collaboration of genetic and feto-maternal services.

Heterozygous ATR Mutations in Mismatch Repair–Deficient Cancer Cells Have Functional Significance

ATR (ataxia telangiectasia and Rad3-related) function is necessary for the proper response to commonly used chemotherapeutic agents. Heterozygous truncating mutations in exon 10 of the ATR gene have been described in numerous cancers exhibiting microsatellite instability. We show that truncating mutations of ATR are capable of acting in a dominant-negative manner to abrogate ATR-dependent Chk1 phosphorylation and cell-cycle arrests after DNA damage. In addition, endometrial cell lines harboring ATR mutations are defective for ATR-dependent responses. These findings imply that ATR mutations play an important role in the development and clinical behavior of a subset of microsatellite instability-positive endometrial, colon, and stomach cancers.

Recurrence of Mowat–Wilson syndrome in siblings with the same proven mutation

Mowat-Wilson syndrome (MWS) is a mental retardation syndrome associated with distinctive facial features, microcephaly, epilepsy, and a variable spectrum of congenital anomalies, including Hirschsprung disease (HSCR), agenesis of the corpus callosum, genitourinary abnormalities, and congenital heart disease. Heterozygous mutations or deletions involving the gene ZFHX1B (previously SIP1) [OMIM 605802] have recently been found to cause MWS. There have previously been no reports of a sibling recurrence of this syndrome. A brother and sister are described with clinical features of MWS, where both have the same truncating mutation in exon 8 of ZFHX1B. As their parents are phenotypically normal and do not have the mutation in lymphocyte-derived DNA, the most likely explanation is germ-line mosaicism.

Double frameshift mutations in APC and MSH2 in the same individual

Heterozygous germline DNA mismatch repair gene mutations are typically associated with HNPCC. Here we report the case of a proband whose father was known for familial adenomatous polyposis. The number of polyps (less than ten) was not typical of polyposis; therefore, the diagnosis of HNPCC was entertained. Microsatellite instability analyses were performed on peripheral blood and biopsy of a right-sided dysplastic adenoma. The tumour tissue showed high-grade instability, and subsequently, immunohistochemistry showed that neither MSH2 nor MSH6 proteins were expressed in tumour cells. Prophylactic colectomy was performed, and an adenocarcinoma developing within the adenoma was diagnosed (pT1N0). Genomic DNA analysis revealed a novel mutation in MSH2 as a frameshift mutation in exon 7 (c.1,191_1,192dupG). Both parents of the proband were analyzed for MSH2 and APC mutations, and in the father, a truncating mutation in exon 15 of APC was identified as del3471-3473GAGA. This mutation was found to be present in the proband. His mother was found to bear the MSH2 exon 7 mutation. At follow-up, the proband was diagnosed with fundic, antral and duodenal adenomas (one fundic adenoma showed low-grade dysplasia). Several tubular rectal adenomas with low-grade dysplasia were excised. The patient later developed an intra-abdominal desmoid tumour.

Double frameshift mutations in APC and MSH2 in the same individual

Heterozygous germline DNA mismatch repair gene mutations are typically associated with HNPCC. Here we report the case of a proband whose father was known for familial adenomatous polyposis. The number of polyps (less than ten) was not typical of polyposis; therefore, the diagnosis of HNPCC was entertained. Microsatellite instability analyses were performed on peripheral blood and biopsy of a right-sided dysplastic adenoma. The tumor tissue showed high-grade instability, and a subsequent, immunohistochemistry showed that neither MSH2 nor MSH6 proteins were expressed in tumor cells. Prophylactic colectomy was performed, and an adenocarcinoma developing within the adenoma was diagnosed (pT1N0). Genomic DNA analysis revealed a novel mutation in MSH2 as a frameshift mutation in exon 7 (c.1191_1192dupG). Both parents of the proband were analysed for MSH2 and APC mutations, and in the father, a truncating mutation in exon 15 of APC was identified as del3471-3473GAGA. This mutation was found to be present in the proband. His mother was found to bear the MSH2 exon 7 mutation. At the follow-up, the proband was diagnosed with fundic, antral and duodenal adenomas (one fundic adenoma showed low-grade dysplasia). Several tubular rectal adenomas with low-grade dysplasia were excised. The patient later developed an intra-abdominal desmoid tumor.

Germline E-cadherin gene mutation screening in familial gastric cancer kindreds

To evaluate the frequency and nature of E-cadherin gene (CDH1) germline mutations in familial gastric cancer kindreds of china. Five familial gastric cancer kindreds of Chinese origin were screened for germline CDH1 mutations, all of them meeting the clinical criteria for hereditary diffuse gastric cancer (HDGC), by PCR-DHPLC and direct sequencing. A new truncating mutation in exon 10 in B family was identified, producing a stop codon at position 503 (Q503X), resulting in a truncated protein. The proband of this family had metachronous development of lobular breast and diffuse type gastric carcinoma. No protein expression was detected in the lobular breast carcinoma, indicating complete inactivation of the gene. A Chinese gastric cancer family with CDH1 germline truncating mutation is described for the first time, and our findings suggest that lobular breast carcinoma might be part of the tumor spectrum of HDGC.

First genotype characterization of Argentinean FAP patients: identification of 14 novel APC mutations.

We examined the adenomatous polyposis coli (APC) gene for disease-causing mutations in 51 unrelated Argentinean probands affected by familial adenomatous polyposis (FAP). Using a combination of the protein truncation test, the single strand conformation polymorphism technique, DNA sequencing and quantitative PCR analysis, we identified the specific mutation in 39 (average age: 28.4 years) of the 51 probands (detection rate: 76.47%); 13 are novel germline mutations and one is a novel sequence variant. There were 27 small deletions, four small duplications, five nonsense mutations in exon 15, three nonsense mutations in exons 6, 11, and 12, and one sequence variant in exon 3 identified in a patient bearing a truncating mutation in exon 15. The most common mutation (found in 10 cases) was at codon 1309. All patients negative for APC mutations were also negative for the MutY homolog (MYH) gene mutation, as expected because of fully penetrant FAP cases. This study enlarges the spectrum of APC gene mutations, and reinforces the concept of mutation heterogeneity. It also sheds light on correlations between the site of APC germline mutations and the clinical manifestations of FAP. Our data indicate that the genotype/phenotype correlations in Argentinean patients are similar to those observed in other populations.

BRCA2 mutation in a family with hereditary prostate cancer

Hereditary prostate cancer is a genetically heterogeneous disease, and so far four different susceptibility loci have been identified. Reports of associated cancers are few, and it is generally considered a site-specific disease. However, some reports have shown an elevated risk for prostate cancer among BRCA2 mutation carriers. In this report, we present a family in which the father and four of his sons were diagnosed with prostate cancer at exceptionally early ages (51, 52, 56, 58, and 63 years, respectively). In addition, three daughters were diagnosed with breast cancer between the ages of 47 and 61. In this family, a truncating mutation in exon 11, 6051delA of the BRCA2 gene, leading to an early termination of the protein (codon 1962), was identified. Although BRCA2 is probably responsible only for a very small fraction of hereditary prostate cancers, this finding supports previous reports of an increased risk of prostate cancer in BRCA2 mutation carriers.

Novel mutations and the emergence of a common mutation in the SDHD gene causing familial paraganglioma.

Familial paragangliomas (PGL) are slow-growing, highly vascular, generally benign neoplasms, usually of the head and neck, that arise from neural crest cells. This rare autosomal dominant disorder is highly penetrant and influenced by genomic imprinting through paternal transmission. Timely detection of these tumors may afford the affected individual the opportunity to avoid the potential serious morbidity associated with surgical removal and the mortality that may accompany local and distant metastases. Linkage to two distinct chromosomal loci, 11q13.1 and 11q23, has been previously reported. Recently, germline mutations in SDHD, a mitochondrial complex II gene on chromosome 11q23, have been demonstrated. We evaluated members of seven families with PGL, five previously studied and shown to have linkage to chromosome 11q23. The entire coding region of the SDHD gene was sequenced and yielded four novel mutations and one mutation shared in three of our unrelated families. Novel mutations found included a truncating mutation in exon 2, as well as a missense mutation, a deletion, and an insertion in exon 4. Three of our families had a common mutation in exon 3 (P81L) that has been reported and thought to be a founder mutation. A restriction enzyme assay was developed for initial screening of this mutation. Molecular analysis is now available and recommended for presymptomatic diagnosis in those at-risk individuals and for confirmatory diagnosis in those having PGL.

BRCA1 mutation analysis in breast/ovarian cancer families from Greece

Germline mutations in BRCA1 gene account for varying proportions of breast/ovarian cancer families, and demonstrate considerable variation in mutational spectra coincident with ethnic and geographical diversity. We have screened for mutations the entire coding sequence of BRCA1 in 30 breast/ovarian cancer women with family history of two or more cases of breast cancer under age 50 and/or ovarian cancer at any age. Genomic DNA from patient was initially analyzed for truncating mutations in exon 11 with PTT followed by DNA sequencing. In the cases where no frameshift mutation was observed in exon 11, all other exons were screened with direct sequencing. Two novel (3099delT, 3277insG) and three already described (3741insA, 1623del5-TTAAA, 5382insC-twice) truncating mutations were identified. In addition, 6 point mutations (L771L, P871L, E1038G, K1183R, S1436S, S1613G) which are already classified as polymorphisms were identified. Three unclassified intronic variants (IVS16-68 G>A, IVS16-92 G>A, IVS18+65G>A) were also detected. These results show that BRCA1 deleterious mutations are present in a fraction (20%) of Greek breast/ovarian cancer families similar to other European countries. Mutations were detected in high- (>/=3 members) as well as in moderate-risk (2 members) families. This is the first report of BRCA1 mutation analysis in Greece.

A review of biochemical and molecular genetic aspects of tyrosine hydroxylase deficiency including a novel mutation (291delC).

An overview is given of the current knowledge on the human tyrosine hydroxylase gene and on the biochemical aspects of diagnosing defects in this gene. Diagnostic biochemical findings are described in four cases of genetically confirmed tyrosine hydroxylase deficiency. Decreased CSF levels of homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG), together with normal pterin and CSF tyrosine and 5-hydroxyindoleacetic acid (5-HIAA) concentrations are the diagnostic hallmarks of tyrosine hydroxylase deficiency. At the metabolite level the diagnosis can only be made reliably in CSF. Strict adherence to a standardized lumbar puncture protocol and adequate reference values are essential for diagnosis of this 'new' treatable neurometabolic disorder. Measurements of HVA, vanillylmandelic acid (VMA) or catecholamines in urine are not relevant for diagnosing tyrosine hydroxylase deficiency. The diagnosis should be considered in all children with unexplained hypokinesia and other extrapyramidal symptoms. Three of our patients are homozygous for a mutation in exon 6 (698G > A) of the tyrosine hydroxylase gene and one patient was compound heterozygous for the same mutation and a novel truncating mutation in exon 3 (291delC).

Classification of Familial Adenomatous Polyposis: A Diagnostic Nightmare

Classification of Familial Adenomatous Polyposis: A Diagnostic Nightmare